13,330 research outputs found
Small size pentaquark width: calculation in QCD sum rules
The pentaquark width is calculated in QCD sum rules. The higher dimension
operators contribution is accounted. It is shown, that should
be very small, less than .Comment: 10 peges, 7 figure
Perturbation of a lattice spectral band by a nearby resonance
A soluble model of weakly coupled "molecular" and "nuclear" Hamiltonians is
studied in order to exhibit explicitly the mechanism leading to the enhancement
of fusion probability in case of a narrow near-threshold nuclear resonance. We,
further, consider molecular cells of this type being arranged in lattice
structures. It is shown that if the real part of the narrow nuclear resonance
lies within the molecular band generated by the intercellular interaction, an
enhancement, proportional to the inverse width of the nuclear resonance, is to
be expected.Comment: RevTeX, 2 figures within the file. In May 2000 the title changed and
some minor corrections have been don
Calculation of the pentaquark width by QCD sum rule
The pentaquark width is calculated in QCD sum rules. Result for
show, that can vary in the region less than
1. The main conclusion is, that if pentaquark is genuine states then sum
rules really predict the narrow width of pentaquark , and the
suppression of the width is both parametrical and numerical.Comment: 8 Ppages, 3 figures,the numerical error was corrected, two figures
are modified. In the limit of errors the result did not change significantl
Nuclear Schiff moment in nuclei with soft octupole and quadrupole vibrations
Nuclear forces violating parity and time reversal invariance (-odd) produce -odd nuclear moments, for example, the
nuclear Schiff moment. In turn, this moment can induce the electric dipole
moment in the atom. The nuclear Schiff moment is predicted to be enhanced in
nuclei with static quadrupole and octupole deformation. The analogous
suggestion of the enhanced contribution to the Schiff moment from the soft
collective quadrupole and octupole vibrations in spherical nuclei is tested in
this article in the framework of the quasiparticle random phase approximation
with separable quadrupole and octupole forces applied to the odd Ra
and Rn isotopes. We confirm the existence of the enhancement effect
due to the soft modes. However, in the standard approximation the enhancement
is strongly reduced by a small weight of the corresponding "particle + phonon"
component in a complicated wave function of a soft nucleus. The perspectives of
a better description of the structure of heavy soft nuclei are discussed.Comment: 27 pages, 3 figures, minor corrections in references adde
Temperature dependence of contact resistance of Au-Ti-Pd2Si-n+-Si ohmic contacts
We investigated temperature dependence of contact resistance of an
Au-Ti-Pd2Si ohmic contact to heavily doped n+-Si. The contact resistance
increases with temperature owing to conduction through the metal shunts. In
this case, the limiting process is diffusion input of electrons to the metal
shunts. The proposed mechanism of contact resistance formation seems to realize
also in the case of wide-gap semiconductors with high concentration of surface
states and dislocation density in the contact
Potential energy and dipole moment surfaces of H3- molecule
A new potential energy surface for the electronic ground state of the
simplest triatomic anion H3- is determined for a large number of geometries.
Its accuracy is improved at short and large distances compared to previous
studies. The permanent dipole moment surface of the state is also computed for
the first time. Nine vibrational levels of H3- and fourteen levels of D3- are
obtained, bound by at most ~70 cm^{-1} and ~ 126 cm^{-1} respectively. These
results should guide the spectroscopic search of the H3- ion in cold gases
(below 100K) of molecular hydrogen in the presence of H3- ions
Pair plasma relaxation time scales
By numerically solving the relativistic Boltzmann equations, we compute the
time scale for relaxation to thermal equilibrium for an optically thick
electron-positron plasma with baryon loading. We focus on the time scales of
electromagnetic interactions. The collisional integrals are obtained directly
from the corresponding QED matrix elements. Thermalization time scales are
computed for a wide range of values of both the total energy density (over 10
orders of magnitude) and of the baryonic loading parameter (over 6 orders of
magnitude). This also allows us to study such interesting limiting cases as the
almost purely electron-positron plasma or electron-proton plasma as well as
intermediate cases. These results appear to be important both for laboratory
experiments aimed at generating optically thick pair plasmas as well as for
astrophysical models in which electron-positron pair plasmas play a relevant
role.Comment: Phys. Rev. E, in pres
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